CD A: This career development award (CDA) will enable Dr. Donahue (PI) to continue the work on Alzheimer's disease (AD) that he began during his fellowship in neuropathology and extend it to involve the blood-brain barrier (BBB). His long-term goal is to lay down the scientific groundwork for therapy of neurologic diseases like AD. A program of coursework, seminars, workshops, and laboratory experience in the academically-rich Brown University environment will go on concurrently with the research plan, leading to independence. As both a neurologist and neuropathologist, he is ideally-suited to perform translational AD research. Background: While there is a growing body of evidence to indicate that the BBB is compromised in AD, there has been little data to support a link between known risk factors for AD and the BBB. Yet, apolipoprotein E (apoE) is critical for maintaining integrity of the BBB, and the apoE4 allele has been shown to be an independent risk factor for developing AD. A preliminary study revealed downregulation of the low- density lipoprotein receptor-related protein (LRP)-1 and upregulation of the receptor for advanced glycation endproducts (RAGE) in the microvessels of AD brains, leading to increased A[unreadable] influx into the brain, further worsening the cerebral A[unreadable] burden. Hypothesis: the product of the e4 allele of the APOE gene somehow fails to maintain the integrity of the BBB, compared to the e3 allele, through both permeability and transport mechanisms. Objectives: (1) quantitate BBB permeability in human apoE3/E4 and apoE KO transgenic mice utilizing the in situ brain perfusion technique; (2) determine the distribution and quantity of A[unreadable] and its BBB transporters LRP-1 and RAGE in the cerebral microvasculature of those same transgenic mice utilizing immunohistochemistry, ELISA, Western blot, and RT-PCR as appropriate. Significance: The ultimate goal of this proposal is to change the way we think about the BBB and AD by providing a quantitative, physiologic characterization of the BBB in these human apoE and apoE KO transgenic mice. Insight will be provided into the mechanisms of apoE maintaining the BBB, as well as the roles that apoE4 may play in predisposing a brain to develop AD when the BBB is compromised via both the permeability and transport pathways. Hopefully, this will lead eventually to treatment interventions to slow the progression and/or reverse the pathophysiology of BBB collapse in AD. [unreadable] [unreadable] [unreadable]